Suppose a guest comes to a different conclusion (5)

I believe the answer is:

guess

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'suppose' is the definition.
(I know that suppose can be written as guess)

I cannot understand how the remainder of the clue works.

(Other definitions for guess that I've seen before include "Imagine" , "Hypothesis" , "Speculation" , "Estimate roughly" , "Surmise" .)

I've seen this clue in the Evening Standard.

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